Neutrophils are the most effective barrier in preventing the invasion and spreading of microorganisms within the human body. Failure of neutrophils to promptly arrive at sites of infection or inflammation can result in uncontrollable infections, while overzealous neutrophilic infiltration can unnecessarily damage normal tissues and impair organ function e.g. in severe forms of asthma and arthritis, acute hepatitis, or ischemia-reperfusion injury. It is our long term goal to elucidate the cellular-level mechanisms involved in directional sensing in neutrophils as a necessary prerequisite to the development of rational therapeutic approaches capable of fine tuning the neutrophil responses appropriate to the disease state. Previous observations from our group have suggested that two distinct sensing mechanisms could be simultaneously responsible for neutrophil directional migration, one spatial, for sensing the asymmetry in space of the micro-environment surrounding the cells, and one temporal, for sensing the changes in time of concentration of the stimuli. The driving hypothesis for this study is that neutrophils synergistically combine the two sensing mechanisms, spatial and temporal, for optimized migratory responses in complex environments. The particular challenge for testing this hypothesis is about how to decouple the spatial and temporal components, knowing that the movement of the neutrophil in spatial chemical gradient results in a temporal change in the concentration at the cell level, and any temporal change of chemokine concentration in a diffusive space also affects the spatial gradients. To address this challenge, we will develop a computer controlled microfluidic device that will continuously altering the conditions in which the neutrophil move to achieve a cancellation of the temporal stimulus that moving neutrophil would otherwise experience. This new technology is unique because it is the first active chemotaxis device, able to lock a chemical gradient on a moving neutrophil target. The technology is also radically different from the traditional, passive chemotaxis devices that have the same gradient, regardless of cell motility. By linking extracellular perturbations and cellular responses through external feed-back loops we will decouple the effects of spatial and temporal stimuli, and be able for the first time to identify and measure the individual contribution of the spatial and temporal components of the neutrophil sensing mechanism. This new knowledge will broaden our understanding of the neutrophil responses in the context of dynamic inflammatory processes and in the context of current knowledge of the molecular biology of the neutrophil will help us develop novel approaches to the prevention and treatment of infectious and inflammatory diseases. PUBLIC HEALTH RELEVANCE: How neutrophils are able to respond to a wide variety of stimuli is not entirely known. Despite the fact that most of the molecules involved in intracellular signaling have been identified, we still do not know how all these molecules work together when neutrophils move in response to gradients of inflammatory signals. To better study these mechanisms at systems level, we will develop a computer controlled microscale system for precise stimulation of the cell while they are moving. Discerning the mechanisms of gradient sensing in neutrophil could open the possibility for new drugs to treat infections with bacteria that are becoming drug resistant, or avoid the destruction neutrophils could cause if unchecked during sterile inflammation like asthma, arthritis, or ischemia-reperfusion injury.